1. Field of the Invention
The present invention relates to a video quality abnormality detection method, and apparatus, for detecting a quality abnormality of a video reproduced by a video device or a video transmitted through a provided communication channel.
2. Description of the Related Art
Those who are engaged in providing or transmitting television videos are obligated to deliver videos of high quality to customers. Television video providers, such as broadcasting stations, often reproduce recorded videos and broadcast them. In such a case, it is necessary to always monitor a reproduced video to determine whether there has occurred an abnormality in the reproduced video. Furthermore, communication companies transmitting television videos need to always monitor the television video to determine whether there has occurred an abnormality in video quality due to an abnormality on the transmission channel.
Heretofore, therefore, a video which is being provided is displayed on a monitor device. A person in charge always monitors the displayed video, and detects a video quality abnormality. If an abnormality is detected, then switchover to a stand-by video device is conducted for reproduction or switchover to a stand-by channel is conducted for transmission.
In the above described way of detection of a video quality abnormality, however, mental and physical burdens of the person in charge are heavy. Furthermore, there is a problem that there are differences in quality abnormality detection between individuals. There is also a problem that the above described way is economically disadvantageous. A method for detecting a quality abnormality mechanically without using a person has been studied. However, a quality abnormality detection apparatus which can be actually used has not yet been proposed.
In view of the above described conventional technique, the present invention has been made. An object of the present invention is to provide a quality abnormality detection method, and apparatus, capable of digitally analyzing a television signal and detecting a video quality abnormality.
To accomplish the above object, the present invention is characterized in that a video quality abnormality detection method comprises: dividing a digitized video signal into a plurality of blocks, normalizing an original signal with each of divided blocks, as a unit, so as to make a power sum of an AC component constant, deriving a power spectrum on the basis of data resulting from the normalizing, deriving a fluctuation value from an approximate straight line of the power spectrum and the power spectrum, and detecting the video quality abnormality from at least a variance of the signal of the block, coefficients of the approximate straight line, and the fluctuation value of the power spectrum.
Secondly, the present invention is characterized in that a video quality abnormality detection apparatus comprises: storage means for storing a digitized luminance signal and a color-difference signal, variance value computation means for dividing the luminance signal and the color-difference signal stored in the storage means into blocks, and deriving variance values of each block, normalization means for deriving normalized signals each having a constant variance value, on the basis of the variance values derived by the variance value computation means, self-correlation function correction processing means for deriving average self-correlation functions within the block from the normalized signals outputted from the normalization means, folding back each of the average self-correlation functions to a negative side, and making the average self-correlation functions over a predetermined section equal to 0 or nearly 0, power spectrum straight line approximation means for conducting Fourier transform on the self-correlation functions derived by the self-correlation function correction processing means, deriving power spectra, and approximating the power spectra by straight lines, fluctuation value computation means for deriving fluctuation values of the power spectra from the approximate straight lines, and a means for making a determination on video abnormality on the basis of the variance values derived by the variance value computation means, coefficients of the approximate straight lines derived by the power spectrum straight line approximation means, and the fluctuation values derived by the fluctuation value computation means.
According to the invention, it becomes possible to make a determination as to whether the video is normal or abnormal in real time mechanically without intervention of a person.